This invention relates to printing processes involving lenticular lens material and, more particularly, to such a printing process in which a thin sheet lenticular lens material is used and in which high quality printing, with desired optical effects, is achieved.
Lenticular lenses are known and used in the printing industry primarily in the printing of advertising and promotional materials, packaging labels, hang tags for merchandise, product tags, and security labels. A preliminary step in a printing process includes selecting segments from two or more visual images used to create a desired visual effect and interlacing these segments. The interlaced segments are then mapped to a selected lenticular lens material in a prepress operation, so when the segments are printed on the material the final result exhibits a desired visual effect such as zoom-in, zoom-out, stereoscopic or 3-dimensional, and movement. The lenticular lens material used in this printing process includes a transparent web which is flat on one side with a plurality of lenticules being formed on the other side. The mapped images are printed directly onto the flat side of the lens material. The lenticules comprise convex lenses formed in a side-by-side arrangement with the lenticules extending parallel to each other the length of the web. Different lens materials have a different number of lenticules per inch (LPI) with the particular LPI selected depending upon the particular application. Once the image segments and material is selected, the previously noted prepress operation is performed with the image segments being mapped with respect to the focal points of the lenticules on the selected lens material.
The major cost component in a lenticular printing operation is the lens material. Heretofore, the lens material has typically been between 20-25 mils thick and the material cost has represented 50-75% of the total cost of a printing project. It is therefor beneficial to try to reduce the cost of the lenticular lens material, if this can be done without sacrificing the quality of the printed product. One way of reducing cost is to decrease the thickness of the lens material. However, doing so creates significant problems which must be overcome to produce a quality product. For example, even though sheet thickness is reduced, the LPI of the material is actually increased. This means that the width of each lenticule is narrower which, in turn, reduces the margin of error which is acceptable during printing. Factors such as temperature, humidity, uniformity of pressure exerted on the material as it is drawn through the printing press, all also have a greater impact on the quality of the printed material than with a conventional thicker lens material. Non-uniform pressure will cause a thin lens material to stretch, distorting the material and causing the printed pattern to no longer be aligned with the focal points of the individual lenses. Similarly, if the temperature and humidity to which the lens material is subjected is not maintained at a constant value, the material will again distort with an unacceptable result being produced.
Overall, and in accordance with the present invention, the quality of the printing operation has been found to be best controlled by meticulously controlling the alignment of the film, printing plates, and lens material prior to the start of printing. In addition, by controlling the pressure on the material as it is run through the press, the temperature and humidity in the area where the press is located, distortions which may occur during printing are further minimized or eliminated altogether. The printing process of the present invention overcome the numerous problems which must be addressed during press set-up and the subsequent printing operation so the result is a printed sheet of lenticular lens material which has the clarity and color delineation required to produce the visual effects desired by the customer.